Carburetor



May 3, 1966 J. T. BICKHAUS ETAL CARBURETOR 3 Sheets-Sheet l INVENTORS JAMES T. BICKHAUS FORREST W. COK

MN N AGENT May 3, 1966 J. T. BICKHAUS ETAL 3,

CARBURETOR Filed July 8, 1963 5 Sheets-Sheet 2 FIG.3.

United States Patent 3,249,346 CARBURETOR James T. Bickhaus, Granite City, Ill., and Forrest W.

Cook, Webster Groves, Mo., assignors to ACF Industries, Incorporated, New York, N. a corporation of New Jersey Filed July 8, 1963, Ser. No. 293,411 11 Claims. (Cl. 261-50) This invention is directed to an air valve carburetor of the type having an air and fuel mixture conduit through the carburetor body. Within the mixture conduit is mounted a manually operated throttle valve for movement between an open and closed position. Upstream from the throttle valve is mounted within the mixture conduit an air v-alve structure, which measures the flow of air through the carburetor to meter the, fuel flowing to the engine. The presence of the air valve also provides a subatmospheric pressure in the region of the fuel nozzles to draw fuel into the mixture conduit.

In some air valve carburetors of this type, a servo mofor positions the air valve in response to the air pressure drop across the air valve such that the angular position of the air valve is a measure of the air flow to theengine. The air valve is connected directly to a device for metering fuel to the engine, so that fuel flow is proportional to the air flow to the engine.

The fuel metering device consists of a metering rod having a portion shaped to provide a flow through a jet restriction in a fuel passage from the fuel bowl of the carburetor to the mixture conduit. The metering rod portion extends through the jet restriction. The other end of the metering rod is directly attached to the air valve for simultaneous operation. As the air valve is moved, the shaped portion of the metering rod in the jet restriction provides an increasing fuel flow with an increasing opening of the air valve.

A disadvantage in the operation of this type of air valve carburetor, is thatduring cranking of the engine there is insufficient manifold vacuum or depression established to open the air valve to the extent necessary to position the metering rod in the jet restriction to provide the maximum flow of fuel required during this cranking operation. -Furthermore, during cranking, it is undesirable to open the air valve to any extent, but rather it is preferably to take advantage of the closed air valve to provide a choking action to draw a maximum amount of fuel into the fuel conduit.

Accordingly, it is an object of this invention to provide a novel air valve carburetor, which during cranking will provide a maximum or an optimum enriched fuel mixture for the starting of the engine.

It is another object of this invention to provide a novel air valve carburetor having a metering rod operative directly with the air valve, which will provide an enriched starting mixture requisite for the starting of the engine.

It is a further object of this invention to provide a novel carburetor having an air valve connected to a fuel metering rod to provide an increasing flow of fuel to the engine with an increasing opening of the air valve and also to provide a maximum fuel and fuel ratio mixture to the engine when the air valve is in closed position during cranking.

The invention is to an air valve carburetor in which the position of the air valve of the carburetor is determined by the flow of air through the carburetor to the engine. Means are provided for controlling the position of the air valve so that it forms a measure of the air flow. A metering rod is connected directly to the air valve to be operated thereby and to also control the flow of fuel to the mixture conduit. The relationship of the meten ing rod and the air valve is such that as the air valve 3,249,346 Patented May 3, 1966 "ice opens to a greater extent in response to a greater flow of air to the engine a correspondingly greater flow of fuel takes place into the mixture conduit of the carburetor. The invention is in the use of an air valve for engine choking action during the cranking of the engine. To provide the maximum fuel to air ratio required for starting, the metering rod is designed and shaped so that when the air valve is in its substantially closed or engine choking position, there is a minimum portion of the metering rod within the metering jet of the fuel of the fuel passage. This provides a maximum flow of fuel to the engine under cranking conditions to provide the appropriate starting mixture.

FIGURE 1 is a plan view partly in section of an air valve carburetor in accordance with the invention.

FIGURE 2 is a side view in elevation of the carburetor of FIGURE 1 showing a portion of an air filter and an engine manifold to which the carburetor is attached.

FIGURE 3 is a sectional view of the carburetor of FIGURE 1 along the lines 33.

FIGURE 4 is a sectional view of the carburetor of FIGURE 1 along section lines 44.

FIGURE 5 is a sectional view of the carburetor of FIGURE 1 along lines 55.

IFIGURES 6, 7, and 8 are enlarged partial views of the fuel control metering rod of FIGURE 4 in different stages of carburetor operation.

The carburetor shown in "the figures has a body casting portion 10, which is connected at a flanged end 12 to an intake manifold structure 13 of engine E shown in FIGURES 2 and 3. The other end of the carburetor body supports a cover casting 19 formed with an air horn section 14 mounting an air filter 15, through which. air passes into the carburetor. tor body 10 from the air horn 14 are a pair of air and fuel mixture conduits 16 and 17 (FIG. 1) each opening at one end into the intake manifold 13 at 18 and through which air from the air filter 15 passes to the engine.

Mounted in the manifold ends of mixture conduits 16 and 17 respectively are throttle valves 20 and 21, fixed to a common throttle shaft 22 journaled for rotational movement in appropriate bearing surfaces in the carburetor body 10. Fixed to one end of. the throttle shaft 22 is a manually operable lever 24 (FIGURES 1 and 4) for moving the throttles 20 and 2.1 from a closed to an open position. In the closed position, the throttles are across horn passage and extends across the two mixture passages 16 and 17. A pair of apertures 25 and 27 extend inwardly from one edge of the air valve to provide clearance with a pair of nozzle bars 80, when the air valve is opened. Air valve 26 is fixed eccentrically to a shaft 28 journaled in the carburetor body for rotational movement. Shaft 28 extends through the carburetor substantially parallel to the throttle shaft 22. The eccentric mounting of valve 26 is optional as the valve 26 may be balanced by a symmetrical mounting.

A short lever arm 30 (FIGURES l and 3) is fixed to and extends from the air valve shaft 28. Lever arm 30 is loosely connected to one end of an actuating rod 32, the other end of which extends through a passage 33 in body casting 10 and is fixed to a backing plate 34 of a diaphragm assembly 36 of a servo motor 39. The diaphragm assembly consists of a flexible diaphragm 38 of rubber or appropriate material, which has its center fixed Passing through the c-arbureture.

between the pair of plates 34 and 35. The attached end of operating rod 32 may be spun over to lock the plates tightly together with the diaphragm 38 in-between. The peripheral edge of diaphragm 38 is sandwiched between the flanged rim 40 of a spring cup housing 42.: Rim 40 is tightly fastened as by machine screws 41, for example, extending through the housing flange 40 into the adjacent portion of the carburetor body 10. A spring 44 is mounted within the housing 42 with one end abutting the closed end of the housing and its other end biased into contact with the center of plate 35 of the diaphragm assembly. Spring 44 biases the diaphragm assembly 30 in a direction to close the air valve 26.

Diaphragm 38 forms with cup housing 42 a chamber 43 and with body casting 10 a chamber 45. Chamber 43 is sealed except for an air passage 46 extending through the wall and the flange 40 of the spring housing 42 to join a second air passage 47 through the carburetor body. Air passage 47 connects into a branch passage 49 which extends to a port 50'opening into the mixture conduit 17 between the closed position of throttle valve 21 and the air valve 26. The air motor just described and its co-action with the air valve is more fully described and claimed in co-pending application of Forrest W. Cook and James T. Bickhaus, Serial No. 276,499 filed April 29, 1963.

Formed within the body 10 of the carburetor are a pair of fuel bowls 52 and 54 (FIGURES 1, 2 and 4) positioned on opposite sides of the air horn structure 14. Fuel ibowl 52 is adjacent to the mixing conduit 16 and fuel bowl 54 is adjacent to the mixing conduit 17. fuel inlet passage 56 is formed through the body cover casting 19. As shown in FIGURE 1, the fuel passage 56 extends the length of the carburetor to provide fuel access to the two fuel bowls. The fuel passage 56 is connected in any appropriate manner to an inlet fuel line 58 leading from a fuel pump =60 which delivers fuel from a fuel tank 62. The fuel inlet line 58, fuel pump 60 and fuel tank 62 are only schematically shown in FIGURE 1.

Fuel from fuel passage 56 enters each fuel bowl through a short passage '61 having a valve seat, which is controlled by a needle valve 63 operated from a float lever 64 pivoted within each fuel bowl at 66 and having a free end attached to a float '68. The float controlled inlet needle 63 operates in a well-known manner. As the fuel in bowls 52 and 54 reaches a predetermined level, the floats 68 through levers 64 will force the pointed ends of needles 63 into the valve seats to prevent additional flow of fuel into the bowls, respectively.

In the bottom of each fuel bowl there is threaded a fuel jet 70 having a calibrated passage 71 (FIGURE therethrough connected to a fuel passage 72 leading to a respective fuel well 74 or 75 (FIGURES 1 and 5) formed in the carburetor body and in the wall of each of the mixing conduits 16 and 17, respectively. For example, in FIGURE 1 well 74 is indicated as being adjacent to mixing conduit 16, and 75 is adjacent to mixing conduit 17. FIGURE 5 shows the well 74 and main fuel nozzle construction associated with mixing conduit 16, which is identical to similar structure associated with mixing conduit 17.

Mounted in the top of each one of the mixing conduits 16 and 17 is a separate subassembly insert 76 consisting of a pair of fuel tubes and the main nozzle struc- As shown in FIGURE 5, the subassemblies each consist of a block 78 having a tubular cross member 80 fitted in an upper portion of the respective block 78 with its upper open end connecting with the fuel passage 84. Fuel tubes 88 are closed except for a small restriction at their lower end suspended within the fuel wells 74 and 75, respectively. Short tubes are press-fitted into the opposite side of blocks, 78 to form fuel passages leading from passages 84 across passages 82 into respective idle chambers 87. Idle chambers 87 open through ports upstream of the closed positions of throttles 20 and 21, respectively. Short passages 93 connect idle chamber 87 to idle ports 97 opening downstream of throttles 20 and 21, respectively. Idle bleed air and fuel flow through ports 97 is controlled by an idle adjusting screw 101.

Restrictions 89 of predetermined size form air bleed passages from the air horn section'into air passages 90 leading into the upper portion of each well 74 and 75, to provide air flow into the main fuel passages. sages 91 extend from the upper end of the air horn through the fuel bowl cover casting 19 into air passages 92, each respectively connected to tube 85 and idlefuel passage 84. A restrictedportion 94 in each passages 92 and restrictions 81 connecting idle passage 84 to the air horn 14 control the amount of air bled into the idle system.

Within each fuel bowl there is mounted a fuel metering rod 96, which is connected at an upper end to a lever 98 fixed to the portion of air valve shaft 28 extending over the top of each fuel bowl. The lower end of each metering rod 96 is movably mounted in the jet aperture 71 within the fuel bowl. The center portion of metering rod 96 passes through an aperture 97 in the float 68. The lower end of each metering rod 96 has variations in rod thickness, as shown in FIGURE 5, consisting of an end portion 99 of minimum thickness, a tapered portion 103, an intermediate portion 100 of optimum thickness and a tapered portion 102 of varying thickness extending from portion 100 to a minimum thickness portion 105. The connection of metering rod-s 96 to the air valve shaft 28 provides simultaneous operation of the metering rods with the air valve A lever 104 (FIGURE 2) is fixed to the end of throttle shaft 22 opposite to that carrying throttle lever 24. Lever 104 carries a spring biased screw 104 for contacting a fast idle cam 106 freely pivoted on a screw shaft 108 and in an eccentric manner so that gravity will bias the cam 106 in a counterclockwise direction, as viewed in FIGURE 2. A second lever'110 is also freely mounted for rotation on screw shaft 108 and is connected by a link 112 to a control lever 114 fixed to a shaft 116 journaled for free rotation in a cup housing 118, as shown in FIGURES 1 and 2. Control lever 114is also connected by a link 119 to a lever 120 loosely mounted for rotation at one end of valve shaft 28. Fixed at the end of the air valve shaft 28 for rotational movement therewith is a short lever 122 having a portion 124 extending over the lever 120. Control lever 114 servesyas a toggle to prop the air valve open during some portion of the operation of the carburetor. Toggle mechanism 114, 119 and 120 *is more fully described and is claimed in co-pending application, Serial No. 281,-

formed with a main fuel passage 82 and an idle fuel pasv 126 so as to move relative thereto.

175 filed May 17, 1963, of Robert]. Smith.

Also fixed to an intermediate portion of shaft 116 for rotation therewith is a second lever 126 carrying at its free end a tapered metering valve 128. The upper end of valve 128 is pivotally mounted on the free end of a lever The tapered end of the metering valve 128 extends into a restriction 130 having a passage therethrough of predetermined size which leads into an air chamber 132 in the housing 118. Air chamber 132 is connected by an air passage 134 to short passage 136 joined to the air passage 47, as shown in FIG- URE 3. The function of metering valve 128 is more completely explained and is claimed in co-pending application of Forrest W. Cook, J. T. Bickhaus and Robert J. Smith, Serial No. 276,472, filed April 29, 1963. t

A third lever 138 is fixed at the other end of the shaft 116 for rotation therewith. Lever 138 is bifurcated at its Air pas-- free end 140 to receive one end of a bimetallic thermostatic spring 142 fitted into the bifurcation 140 so as to move the lever 138. The other end of spring 142 is fixed v to a stationary shaft 143 mounted on the cup housing 118.

The cup housing 118 is divided into a pair of chambers 145 and 146 by an imperforate wall structure 144 extending-transversely across the housing. This Wall 144 prevents the interference of air flowing through one chamber with the air flowing through the other chamber. Chamber 145 is connected to the atmosphere through a vent schematically indicated at 147 in FIGURE 1. Chamlber 146 is connected to a source of heated air such as a stove connected to the exhaust manifold of the engine. Air from the stove is brought through the hot air conduit and through an inlet fitting 148 into the chamber 146.

Chamber 146 is connected by an air passage 149 to the carburetor flange 12 at a point downstream of the throttle 21. This is shown in specific detail in FIGURE 3.

Because of subatmospheric air pressure condition in the manifold 13 during engine operation, air will flow from the manifold stove through the hot air conduit and fitting 148 into the chamber 146 and from the chamber through passage 149 into the manifold. Also, when the valve 128 is open atmospheric air will flow through vent 147 into chamber 145 and from chamber 145 through passages 132, 134 and '136 into passage 47.

An accelerating pump piston 150 is mounted within a pump cylinder 152 (FIGURE 4) formed at the end of the fuel bowl 54. A one way ball check valve 154 permits a fuel to flow from the fuel chamber into the pump cylinder 152. The piston rod 156 is connected by a linkage 158 pivoted on the cover casting 19 through a link 160 to the throttle lever 24. The accelerating pump provides additional fuel during the opening of the throttle.

When the throttle is opened, the pump piston 150 is pressed downwardly to force fuel through an accelerating fuel passage 162 connected to accelerating nozzles 164 (FIGURE 5) extending into each of the mixture conduits 16 and 17. This provides additional fuel during throttle operation.

In operation, the engine is cranked to operate the fuel pump and to force fuel into the inlet passage 56 of the carburetor. With the float valves in a lowered position, fuel will flow from fuel passage 56 into each of the fuel bowls 54 and 52. Fuel will continue to flow until the floats 68 are raised to a predetermined position, at which point the needle valves 63 are closed to prevent further flow of fuel into the fuel bowl. Fuel will flow from each bowl by gravity through the corresponding metering jet into fuel passages 72 and to a level in each of the fuel wells 74 and 75 equal to the level of fuel in the respective fuel bowl. Fuel will also flow past the check valve 154 to fill the accelerating pump cylinder 152 to the level of fuel in the fuel bowl.

One side of diaphragm 36 of the servo motor 39 is exposed to air pressure within chamber 43, which is connected to port 50 in mixture conduit 17 between air valve 26 and throttle valve 21. The other side of diaphragm 6 carburetor body to the flange 12, at which point passage 186 opens downstream of throttle 20. Upon the starting of the engine manifold vacuum downstream of the throttle is effectivethrough the passage 186 to the motor chamber 182 to quickly draw the diaphragm assembly 181 to the left, as viewed in FIGURE 2. This pulls the linkage rod 174 to the end of slot 172, as shown in FIGURE 2, which moves the air valve to a partially open position of around 20 degrees from its closed position. As long as the engine is operating, the air valve is held to a minimum opening of this amount. This permits sufficient air to pass through the carburetor for engine Warmup as well as idle. The arcuate slot 172 provides a lost motion between the motor linkage rod 174 and the lever 122 so that the air valve can open to a greater amount without opposition of the linkage rod 174.

Engine operation When the engine is running and the throttles are opened from their closed positions, the air pressure at port 50 drops from atmospheric and the air pressure in motor chamber 43 is reduced until diaphragm 36 is pressed inwardly against the bias of spring 44. The air valve 26 then takes a position determined by servo motor 39, in

which the difference in air force on the opposite sides of diaphragm 36 balances the bias of spring 44. As throttles 20 and 21 are moved to change the amount of air flowing to the engine, the servo motor 39 will change the 36 is exposed through passage 33 to substantially atmos- I pheric air pressure in the air horn 14 upstream of air valve 26.

There is provided means for pulling open and holding the air valve open after the engine has started. This is necessary in order that sufficient air will flow to the carburetor to enablethe engine to run and to prevent the air valve from choking the engine. The means (FIGURE 2) consists of a portion 170 of lever 122 formed with an arcuate lost motion slot 172, into which one end of a linkage rod 174 is hooked for operation.- The other end of rod 174 is fixed to the stem 176 of a diaphragm assembly 181 of a small air motor 178. The diaphragm assemposition of air valve 26 to retain substantially the same pressure drop across the air valve. The air valve 26 is thus a device for measuring air flow through the carburetor to the engine.

The value of spring 44 is selected to retain a fixed pressure drop across the air valve. This spring sets the angular position of the air valve relative to the amount of air flowing through the carburetor. This then positions the proper portions of metering rods 96 within jets 70. The shape of metering portions of rods 96 are-calibrated to give sufiicient fuel flow through jets 70 to provide maximum power at wide open throttle at any speed of the engine up to the full air capacity of the carburetors.

The tapered portions 102 of metering rods 96 are shaped to provide an increasing flow of fuel through jets 70 as the air valve opens to full open position, at which opening of the air valve, the rod portions 105 are within jets 70 for maximum fuel flow. The optimum air-fuel ratio is maintained with a full open air valve by the increased depression around the nozzle bars 80 due to increased manifold vacuum at higher speeds.

Cola engine operation When ambient conditions are below a temperature of about 70 F., the theromstatic spring 142 biases lever 138, shaft 116 and lever 114 in a clockwise direction to a position, shown in FIGURES l and 4. In this position, operating lever 114 and link 112 have moved the fast idle cam 106 in a clockwise direction against gravity bias by the aid of a lug 109 fixed to lever 110 in the path of rotation of cam 106. After the engine has started and the throttle lever 24 manually released, the adjustment screw stop,104 on the throttle lever 104 will contact the high portion 107 of the cam 106 and hold the throttles in a slightly open position so the engine will operate at a fast idle speed. The idle speed of the engine provides a subatmospheric pressure within the intake manifold opening 18 in the order of 18 to 20 inches of mercury negative pressure. This negative pressure will be effective upstream of throttles 20 and 21 to cause a depression below air valve 26. This low pressure will be sensed through port 50 and passage 47 to the servo motor 39, which will operate to partially open the air valve 26 and permit flow of sufficient air past throttles 20 and 21 for the cold idle operation.

Idle fuel is drawn from the nozzle ports 83. Also, air passing through apertures 25 and 27 will sweep around the upper edges of the slightly open throttles 20 and 21 and will draw air and fuel from the idle ports 95. The metering rod portions 103 are positioned within jets 70 during this cold engine idling operation.

Under cold engine operation, with shaft 116 biased by spring 142 to its position shown in FIGURES l and 4, the metering valve pin 128 is out of the air restriction 130 so as to provide a bleeding of air through passages 134 and 136 to passage 47 and through passage 49 to the mixture conduit. This air bleed slightly increases the pressure within the servo motor chamber 43' which, with the spring 44, closes the air valve 2 6 slightly from a position it would otherwise have. This results in a higher depression area between the air valve and throttles 20 and 21 which induces a richer fuel flow from the nozzle ports 83 and optimum engine performance for cold engine operation. The amount that valve 26 is closed by the air bled through passages 134 and 136 may be adjustably controlled by the size of a restriction 135 placed in passage 47 between passages 136 and passage 49. This restriction may be in the range of 0.025" to 0.040" in diameter to provide the desired effect.

When the engine has warmed to a normal operating temperature, thermostatic spring 142 has rotated shaft 116 and levers 114 and 110 to their positions indicated in FIGURE 2. When the throttles are now operated, the idle stop screw 104' releases the fast idle cam 106 and permits it to drop by gravity. If the throttles are subsequently released for idling conditions, the screw 104' will contact the lowest cam position 107a (FIGURE 2) and allow the throttles to take a closed position. Idle fuel is now drawn by manifold vacuum mainly from the idle chamber 87 through the idle port 97 and in the manner described above. Air flows through idle bleeds 81 and 91 and the bypass passage 163 controlled by the adjustment screw 165.

Rotation of shaft 116 by spring 142 counterclockwise as viewed in the figures, moves valve needle 128 into orifice 130 to close off the air bleed to passage 47 and eliminate the fuel enrichening effect of this bleed. Simultaneously, operating lever 114 is rotated to the fullest extent in the counterclockwise direction. In this position, the pivot 115 between levers 114 and 119 has passed over center of a straight line between shaft 116 and the pivot117 between levers 119 and 120. i A toggle link is formed by levers 114 and 119, as seen in FIG- URE 2. This over-center toggle condition retains the lever 120 in an uppermost position, where lever arm 124 will strike lever 120. This block-s open the air valve 26 and prevents it from closing when the engine is hot. Thus the engine can be started without an over-rich condition which would be provided with air valve 26 closed. An optimum opening for valve 26 for hot engine starting conditions is from 25 to 30 degrees from its closed position. Also, holding the valve 26 in this open condition allows the engine when warm to function properly during idle operation and without an over-rich fuel mixture. In this blocked open position of the air valve, metering rod portions 100 are positioned within jets 70to provide a sufficient flow of fuel to the engine.

As the engine cools when not running, the thermostatic spring 142 tensions. The lever 114 will be rotated clockwise slowly and will break the toggle stop. The air valve is then closed as lever 120 is slowly rotated clockwise by the cooling of spring 142. When cold, the air valve 26 is closed and in position for a cold start.

Starting During cranking of the engine with the throttle open, the engine turns over to pump air through the carburetor for starting the engine. With the engine cold, spring 44 of the servo motor holds'the air valve 26 in a closed position. During cranking, the engine,.however, turns over so slowly that an insufficient vacuum is produced downstream of the air valve to open it to a degree at which a minimum thickness portion of the metering rod 96 will be in the: jet 70 to permit a maximum flow of fuel required for engine starting. Therefore, in accordance with the invention, the metering rod 96 is formed with a minimum thickness portion 99 at its end and the linkage between the metering rod 96 and the air valve shaft 28 is suchas to position the portion 99 within the jet passage 71 when the air valve is in a. closed position. This arrangement as shown in FIGURE 6 allows the jet passage 71 to be at a maximum opening so that the small low vacuum downstream of the air valve will pull a maximum amount of fuel through the fuel nozzles 83 for starting. The starting mixture of the engine has roughly a fuel to air ratio of l to 1. Thus, the air flowing through openings 25 and 27 in the 'air valve 26 mix with the flow of fuelfrom the nozzle ports 83 to provide the starting mixture- Without the provision of the maximum fuel flow through the restricted jet passage 71 there would be insufficient fuel pulled by the manifoldvacuum during cranking to provide this optimum starting mixture.-

FIGURE 7 discloses the position of metering [rod 96 when the engine has started and while still cold, the airvalve is pulled open by the vacuum break diaphragm air motor 178.: In this position of the air valve, the

metering 'rod 96 is positioned with the tapered portion 103 Within the restricted jet pasasge 71 so as to provide a relatively rich flow of fuel to themixture conduit for cold engine operation. However, after the engine has warmed up, as described previouslyythe thermostatically con trolled valve 128 is closed to modify the action of the servo motor 39 so that the airvalve is opened slightly allowing a greater flow of air to lean out the idle mixture. This further opening of the air valve positions the metering rod portion to maximum thickness within the metering jet passage 71 so as to minimize fuel flow to the engine during idle. Thus, with ia-walrm idle or low speed operation of the engine, an economy fuel and air mixture is provided to the engine for optimum operation. The last condition is shown in FIGURES.

One type of metering rod is shown in the drawings and described above. However, it is obvious th ataother types of metering rods and control structures may be utilized in which the metering control is tied directly into the air valve for simultaneous operation therewith. Whatevery type of metering structure is used, however, it is within the scope of this invention that a maximum flow of fuel is permitted to pass through the metering passage 71 when the air valve is in its closed position which it would take during cranking operation of the engine under cold ambient conditions. Also, the metering rod portions which successively pass through the fuel metering passage 71 in accordance with the movement of the air valve can be shaped to provide whatever operating conditions of the engine is desired as determined by the flow of air through the mixture conduit.

We claim:

1. A carburetor comprising a body structure having an air and fuel mixture conduit the-rethrough, a throttle valve mounted across said mixture conduit. for movement from an open to a position closing said mixture conduit, means for operating said throttle valve, an air valve mounted within said mixture conduit anteriorly of said throttle valve for movement in response vto air flow through said mixture conduit from a position closing said mixture conduit to an open position, a spring connected between said air valve and said carburetor body and biasing said air valve toward a closed position, said carburetor body including a fuel reservoir and B. fuel passage extending from said fuel reservoir to said mixture conduit between said air valve and said throttle valve, means including a movable metering element in said fuel passage for varying the flow of fuel therethrough, said metering element being operatively connected to said air valve to be moved therewith upon the opening and closing movement of said air valve, said element including a portion thereof for providing a maximum flow of fuel through said fuel conduit when said air valve is in a closed position.

2. The invention of claim 1 including motor means responsive to air pressure in said mixture conduit for opening said air valve.

3. A carburetor comprising a body structure having an air and fuel mixture conduit therethrough, a throttle valve mounted across said mixture conduit for movement from an open to a position closing said mixture conduit, means for operating said throttle valve, an air valve mounted within said mixture conduit anteriorly of said throttle valve for movement in response to air flow through said mixture conduit from a position closing said mixture conduit to an open position, a spring connected between said air valve and said carburetor body and biasing said air valve toward a closed position, said carburetor body including a fuel reservoir and a fuel passage extending from said fuel reservoir to said mixture conduit between said air valve and said throttle valve, means including a movable metering rod having a portion extending into said fuel passage for varying the flow of fuel therethroug'h, said metering rod being operatively connected to said air valve to be moved therewith upon the opening and closing movement of said air valve, said metering rod portion including a part thereof for providing a maximum flow of fuel through said fuel conduit when said air valve is in a closed position.

4. The invention of claim 3 including motor means responsive to air pressure in said mixture conduit for moving said air valve and metering rod simultaneously.

5. A carburetor comprising a body structure having an air and fuel mixture conduit therethrough a throttle valve mounted across said mixture conduit for movement from an open to a position closing said mixture conduit, means for operating said throttle valve, an air valve mounted within said mixture conduit anteriorly of said throttle valve for movement in response to air flow through said mixture conduit from a position closing said mixture conduit to an open position, a spring connected between said air valve and said carburetor body and biasing said air valve toward a closed position, said carburetor body including a fuel reservoir and a fuel passage extending from said fuel reservoir to said mixture conduit between said air valve and said throttle valve, means including a metering rod movably mounted on said carburetor and having a plurality of portions thereof positioned for movement into said fuel passage for varying the flow of fuel therethrough, said linkage means connecting said metering rod operatively to said air valve to be moved therewith upon the opening and closing movement of said air valve, said linkage means positioning one of said metering portions within said fuel passage for providing a maximum flow of fuel through said fuel conduit when said air valve is in a closed position.

6. The invention of claim 5 including an air motor means connected to said mixture conduit downstream of said air valve and responsive to air pressure in said mixture conduit to open said air valve and move other of said rod portions into said fuel passage to vary fuel flow to said mixture conduit.

7. A carburetor comprising a body structure having an air and fuel mixture conduit therethrough, a throttle valve mounted across said mixture conduit for movement from an open to a position closing said mixture conduit, means for operating said throttle valve, an air valve mounted within said mixture conduit anteriorly of said throttle valve for movement in response to air fiow through said mixture conduit from a position closing said mixture conduit to an open position, a spring connected between said air valve and said carburetor body and biasing said air valve toward a closed position, said carburetor body including a fuel reservoir and a fuel passage extending from said fuel reservoir to said mixture conduit between said air valve and said throttle valve, a metering rod having a portion of varying thickness positioned in said fuel passage for varying fuel flow therethrough, means connecting said metering rod to said air valve for simultaneous movement therewith, said metering rod portion varying in thickness from a maximum to aminimum thickness, said connecting means positioning said metering rod portion of minimum thickness within said fuel passage when said air valve is in an open position and arranged to move said metering rod portion of maximum thickness into said fuel passage as said air valve is closed from said open position, said metering rod portion having a second region of minimum thickness positioned within said fuel passage when said air valve is in closed position.

8. The invention of claim 7 including motor means responsiveto air pressure said mixture conduit for moving said air valve. 4

9. A carburetor comprising a body structure having an air and fuel mixture conduit therethrough, a throttle valve mounted across said mixture conduit for movement from an open to a position closing said mixture conduit, means for operating said throttle valve, an air valve mounted within said mixture conduit anteriorly of said throttle valve for movement in response to air flow through said mixture conduit from a position closing said mixture conduit to an open position, a spring connected between said air valve and said carburetor body and biasing said air valve toward a closed position, said carburetor body including a fuel reservoir and a fuel passage extending from said fuel reservoir to said mixture conduit between said air valve and said throttle valve, said fuel passage including a restricted portion of predetermined size, a metering rod having portions varying in thickness sequentially from a first small thickness to a larger thickness to a second small thickness, means connecting said metering rod to said air valve for simultaneous movementtherewith, said connecting means positioning said metering rod portion of a first small thickness within said restricted fuel passage portion when said air valve is in a closed position, said connecting means moving said metering rod in accordance with the progressive opening of said air valve to sequentially position said metering rod portion of larger thickness and of a second small thickness within said restricted passage portion.

10. A carburetor comprising a body structure having an air and fuel mixture conduit therethrough, a throttle valve mounted across said mixture conduit for movement froman open to a position closing said mixture conduit, means for operating said throttle valve, an air valve mounted within said mixture conduit anteriorly of said throttle valve for movement in response to air flow through said mixture conduit from a position closing said mixture conduit to an open position, a spring connected between said air valve and said carburetor body and biasing said air valve toward a closed position, motor means responsive to air pressure within said mixture conduit for opening said air valve, said carburetor body including a fuel reservoir and a fuel-passage extending from said fuel reservoir to said mixture conduit between said air valve and said throttle valve, said fuel passage including a restricted portion of predetermined size, a metering rod having portions varying in thickness sequentially from a first small thickness to a larger thickness to a second small thickness, means connecting said metering rod to said air valve for simultaneous movement therewith, said connecting means positioning said metering rod portion of a first small thickness within said restricted fuel passage portion when said air valve is in a closed position, said connecting means moving said metering rod in accordance with the progressive opening of said air valve by said motor means to sequentially position said metering rod portion of larger thickness and of a second small thickness within said restricted passage portion.

11. A carburetor comprising a body structure having an air and fuel mixture conduit therethrough, a throttle valve mounted across said mixture conduit for movement from an open to a position closing said mixture conduit, means for operating said throtle valve, an air valve shaft rotatably mounted across said mixture conduit anteriorly of said throttle valve, an air valve eccentrically fixed to said air valve shaft for movement in response to air flow through said mixture conduit from a position closing said mixture conduit to an open position, a spring connected between said air valve shaft and said carburetor body and biasing said air valve toward a closed position, airtmotor means connected to said air valve shaft and responsive to air pressure within said mixture conduit downstream of said air valve to rotate said air valve shaft against the bias of said spring to open said air valve, said carburetor body including a fuel reservoir and a fuel passage extending from said fuel reservoir to said mixture conduit between said air valve and said throttle valve, said fuel passage including a restricted portion of predetermined size, a metering rod having portions varying in thickness sequentially from a first small thickness to a larger thickness to a second small thickness, means connecting said metering rod, to said air valve shaft for simultaneous movement therewith, said connecting means positioning said metering rod portion of a first small thickness within said restricted fuel passage portion when said air valve is in a closed position, said connecting means moving said metering rod in accordance with the progressive opening of said air valve to sequentially position said metering rod portion of larger thickness and for a second small thickness Within said restricted passage portion,

References Cited by theExaminer,

UNITED STATES PATENTS 1,376,707 5/1921 Fehr et al. 26l60 2,675,792. 4/1954 Brown et a1 261--69 X 2,985,159 4/1961 Moseley 261-69 X 3,078,079 2/1963 Mick 26150 X 3,190,622 6/1965 Sarto 2615l X HARRY B. THORNTON, Primary Examiner.

T. R; MILES, Assistant Examiner; 

1. A CARBURETOR COMPRISING A BODY STRUCTURE HAVING AN AIR AND FUEL MIXTURE CONDUIT THERETHROUGH, A THROTTLE VALVE MOUNTED ACROSS SAID MIXTURE CONDUIT FOR MOVEMENT FROM AN OPEN TO A POSITION CLOSING SAID MIXTURE CONDUIT, MEANS FOR OPERATING SAID THROTTLE VALVE, AN AIR VALVE MOUNTED WITHIN SAID MIXTURE CONDUIT ANTERIORLY OF SAID THROTTLE VALVE FOR MOVEMENT IN RESPONSE TO AIR FLOW THROUGH SAID MIXTURE CONDUIT FROM A POSITION CLOSING SAID MIXTURE CONDUIT TO AN OPEN POSITION, A SPRING CONNECTED BETWEEN SAID AIR VALVE AND SAID CARBURETOR BODY AND BIASING SAID AIR VALVE TOWARD A CLOSED POSITION, SAID CARBURETOR BODY INCLUDING A FUEL RESERVOIR AND A FUEL 